When a co-worker once saw Bob Keown eating three hamburgers without the buns at lunch, she gasped and said, "You're doing that Atkins diet. That's dangerous." Another told him that if he collapsed at his desk, she would pump him full of carbohydrates intravenously.

Bob Keown, of Decatur, Ga., has been on the Atkins diet for three years and has lost 60 pounds.

By Michael A. Schwarz, USA TODAY

Keown, 39, a health care consultant in Atlanta, has always felt that he had to apologize for following the controversial high-fat, low-carb diet that helped him shed 60 pounds.

Dr. Atkins' New Diet Revolution, updated from its first publication in 1972, appeals to Americans who love their steak, bacon and eggs, but not their fruits and vegetables. Cardiologist Robert Atkins allows dieters to eat hamburger, pork, butter and other high-fat foods and has them cut way back on carbohydrates, including sweets, some starchy vegetables and many fruits.

Food OK on Atkins Plan

Steak

Bacon (Limited to 2 slices)

Pork chops

Fish

Lamb

Chicken

Nuts and seeds (1 or 2 ounces)

Eggs

Cheese (limited to 3 ounces)

Regular high-fat salad dressing

Olive oil and other vegetable oils

Butter

Three to four cups of vegetables such as lettuces (endive, radicchio), asparagus, snow peas, broccoli, spinach, cauliflower and peppers

Fruits such as strawberries, raspberries, melons, peaches

Beverages such as water, club soda, cream (limited to two or three tablespoons a day), decaffeinated coffee or tea

Foods eliminated during weight-loss phase and limited during maintenance phase on the Atkins diet

Sweets (candy, cake, cookies)

Potatoes

Rice

Pasta

Cereals

Crackers

Breads (whole grain, French)

Some vegetables such as peas and corn

Fruits such as bananas, apples, raisins, figs and papayas

Source: Dr. Atkins' New Diet Revolution

For years, nutritionists have raised concerns, because the diet runs counter to the advice of major health organizations, which advocate a diet relatively low in saturated (animal) fat and high in complex carbohydrates (grains and vegetables). Those recommendations are based on scientific evidence that such foods lower the risk of cardiovascular disease and some cancers.

But Keown and other Atkins followers may not have to apologize much longer. Several new studies show that some dieters lose more weight on the Atkins plan than on more conventional low-fat diets. "This research reflects my experience," Keown says. "I've been doing this for over three years, and I feel better and healthier than I did when I was eating lots of carbohydrates."

Critics say the studies are small and the findings are preliminary. They point out that other research indicates that the Atkins diet may increase the risk of kidney stones and bone loss.

And nutrition experts say the Atkins diet is not a practical long-term way to eat. Even the recent studies show that people "start to fade" on the diet at about the third to fifth month, says George Blackburn, director of nutrition at Harvard Medical School. "They just can't go without one of the food groups and be satisfied with the limited variety of foods on this diet."

Yet there is no doubt some dieters find it easier to lose weight on the Atkins diet than on more conventional diets. And many Americans are desperate to drop pounds: Almost 65% of adults in this country weigh too much.

Several years ago, government officials and obesity researchers called for scientific studies on the low-carbohydrate plan, and those results are beginning to trickle in. Among them:

A study of 120 overweight volunteers, conducted at Duke University Medical School and funded by a grant from the Robert C. Atkins Foundation, had patients follow either the Atkins diet or an American Heart Association low-fat plan. Atkins dieters also took multivitamins and fish oil capsules, as the book recommends. After six months, low-fat dieters had lost 20 pounds; the Atkins dieters had lost 31 pounds, and they were more likely to adhere to the diet.

Total cholesterol went down 6% for the low-fat group vs. 4% for the Atkins group. Dieters following the low-fat regimen had a 22% drop in blood fats known as triglycerides and no increase in HDL, or "good" cholesterol. The Atkins dieters experienced a 49% drop in triglycerides and an 11% increase in HDL.

Lead researcher Eric Westman, associate professor of medicine at Duke University Medical Center, says other studies found a similar Atkins effect without fish oil supplements, "so we believe there are effects from both the low-carb diet and the fish oil." But others disagree. Triglycerides "drop like a bomb" when you lose weight, and fish oil has a "major impact" on blood fats, Blackburn says.

In another study, researchers at the University of Cincinnati had 53 obese women, ages 29 to 59, follow either the Atkins diet or a diet that got 30% of calories from fat. In contrast, Atkins dieters typically get about 60% of calories from fat, 30% from protein and 10% from carbohydrates. After six months, the Atkins dieters lost an average 18.5 pounds; the other group, 8.5. Both groups had normal cholesterol and experienced similar improvements in blood fats, says lead researcher Bonnie Brehm, assistant professor of nutrition in the College of Nursing.

Gary Foster, clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine, says the research results so far are preliminary and are not a license to pig out on bacon. "We shouldn't change our dietary guidelines based on a few studies. However, these data suggest that these diets may not be as harmful as we thought."

Foster is the lead researcher on an upcoming study of the Atkins diet sponsored by the National Institutes of Health. The study, to be conducted at three universities, will track 360 participants in an attempt to answer questions on the diet's impact on weight loss, arteries, cholesterol, body composition, kidneys and bones.

Food OK on Atkins Plan

Steak

Bacon (Limited to 2 slices)

Pork chops

Fish

Lamb

Chicken

Nuts and seeds (1 or 2 ounces)

Eggs

Cheese (limited to 3 ounces)

Regular high-fat salad dressing

Olive oil and other vegetable oils

Butter

Three to four cups of vegetables such as lettuces (endive, radicchio), asparagus, snow peas, broccoli, spinach, cauliflower and peppers

Beverages such as water, club soda, cream (limited to two or three tablespoons a day), decaffeinated coffee or tea

Fruits such as strawberries, raspberries, melons, peaches

Beverages such as water, club soda, cream (limited to two or three tablespoons a day), decaffeinated coffee or tea

Foods eliminated during weight-loss phase and limited during maintenance phase on the Atkins diet

Sweets (candy, cake, cookies)

Potatoes

Rice

Pasta

Cereals

Crackers

Breads (whole grain, French)

Some vegetables such as peas and corn

Fruits such as bananas, apples, raisins, figs and papayas

Source: Dr. Atkins' New Diet Revolution

Scientists also will look at whether it can be more useful for some people than others, and how much people are able to exercise while on the diet. They want to know why dieters seem more likely to stick with the low-carb program than a conventional diet.

One theory: Atkins dieters may eat less because of a loss of appetite resulting from ketosis, in which the body —deprived of carbohydrates — partly breaks down body fat and turns it into fuel. Another theory: People who have initial success on the diet are spurred to stick with it longer.

Atkins spokeswoman Colette Heimowitz says the diet's combination of protein and fat is more filling than a high-carbohydrate meal and avoids the blood sugar swings that high-carb meals can produce.

The plan seems to appeal most to meat-lovers such as Keown. Before he went on the diet, Keown says, he was a really big eater. He'd have a bagel for breakfast and was starving by 9:30, so he'd have another bagel, and another. "I'm not one of those people who is going to tell you that I hardly ate anything," he says.

Keown was up to 238 pounds on his 5-foot-9 frame when his wife told him about a friend who had dropped weight on the Atkins diet, so he decided to give it a try.

At first, he felt miserable. "For the first two days, I was in bad shape. I felt very weak, and my head hurt so bad that my vision blurred. And then it all went away." He followed the strict induction phase for two weeks, then adhered to the ongoing weight-loss phase for six months, losing about 60 pounds in all.

He says he has felt better on this diet than he ever did before. "I wasn't hungry. I'd look up from my desk and it was 3 o'clock and I hadn't eaten lunch."

A few weeks into the plan, Keown began running and started playing more tennis, rugby and street hockey, sometimes for several hours a day. He now weighs 175 pounds. His total cholesterol has dropped from 234 to 191.

Over the past three years,Keown hasn't eaten any junk food and not much starchy fare. No fries, no chips, no cake, no pizza, no bagels. But he has had lots of chicken wings, steaks, hamburgers, butter, pork rinds, eggs and bacon. "They are just heavenly," he says.

Keown has at least one negative side effect: occasional bad breath, perhaps a result of ketosis. "My breath can at times be deadly," he says. "It's a legitimate complaint about the diet, but I'll trade it for not busting out of 40-inch-waist pants."

Not everyone has had Keown's success on the plan. Richard Suisman, 71, a transportation consultant in Washington, D.C., followed the Atkins diet for a year. In the first two months when he was adhering to it rigidly, he lost about eight pounds, and his cholesterol dropped about 30 points. But then he went on the maintenance phase and regained the weight, and his cholesterol went back up to 240.

So he visited a registered dietitian and started a low-fat program that was rich in grains, fruits, vegetables and fish. He lost nine pounds in four months, and his cholesterol dropped 80 points, to 160. He was taking the same cholesterol-lowering drug during both diets.

He thinks the Atkins diet is too restrictive for the long term. "You are always watching yourself." The way he's eating now, he says, is "definitely more practical."

Katherine Tallmadge, a registered dietitian in Washington, D.C., and a spokeswoman for the American Dietetic Association, says she has seen many Atkins dropouts. "I can't imagine eating cheese without bread, crackers or fruit. What fun is it eating hunks of cheese or meat day in and day out?"

Blackburn of Harvard says dieters can get dramatic weight losses without eliminating food groups. "It's the junk food that's killing us, and if people would cut back on the junk food, they'd cut calories, lose weight, improve their blood cholesterol and prevent heart disease and cancer."